Can Isopropyl Alcohol increase the combustability of Gasoline?

Question

Can Isopropyl Alcohol increase the combustability of Gasoline?

Answer 1

Short answer: No.

Clarification: "combustability" is a vague term. Gasoline can burn, in the vapor phase, quite well when it is between 1% and 6% by volume (the remaining 99-94% being air).

If you want to expand those "upper explosive limit" and "lower explosive limit" then add ether ("starting fluid"), not IPA. Hydrogen gas would also work, but is tricky to obtain, transport and handle safely.

If you want to lower the "flash point" (the temperature at which a liquid has enough flammable vapors over it to burn) you'd need to add something that is more volatile. Propane, butane and pentane would work and are, in fact, added to create winter blends of gasolines in snow country. IPA would not work, it would decrease the vapor pressure of a gasoline mixture.

If you want to increase the energy content of the fuel, IPA does the reverse. It already has some oxygen in it so can be thought of as being partially oxidized already. It certainly has fewer BTUs per pound and per gallon than gasoline. Higher molecular weight hydrocarbons nonane, decane, etc) would help but the refinery has already worked hard to balance energy content with cold-starting and smog issues.

IPA would help in two ways:

1) it reduces the carbon monoxide (CO) emissions which is a problem in some areas, especially in winter. Any alcohol (ethanol, methanol, IPA, etc) would. Methyl tertiary-butyl ether (MTBE) was most widely used to do that, but it is hard to get out of the groundwater if spilled. But with any of those, you get lower MPG.

2) it allows higher-compression engines. Because it raises the "auto-ignition temperature" (actually makes the mixture more resistent to burning), the gas-air mix can compressed more. This gives slightly better fuel efficiency and potentially more power from the same displacement engine. Pretty much only used in racing where engine size is fixed and everyone wants more HP.

Hope that helps.

Answer 2

I would think that the addition of IPA would lower the flash point and boiling point of the gasoline, and thereby make it more combustible! Just my opinion.